1. Field of the Invention
The present invention relates to a storage subsystem and a storage controller, both connected to host computers. More particularly, the invention relates to a storage subsystem and a storage controller adapted to provide enhanced performance and reliability.
2. Description of the Related Art
In recent years, storage controllers have been required to provide better performance, higher reliability and greater availability than ever before as computer systems are getting larger in scale to process data at higher speeds than ever before, 24 hours a day and 365 days a year, with data transfer interfaces also enhanced in speed. Illustratively, Japanese Patent Laid-open No. Hei 11-7359 discloses a storage controller incorporating an internal network to improve its performance.
There has been a growing need for connecting a storage controller to a plurality of host computers having multiple interfaces, as shown in FIG. 8. In such a storage controller, a host interface section comprises a host interface for addressing each different host computer. A control processor in each host interface analyzes I/O commands received from the corresponding host computer and exchanges data accordingly with a cache memory 215 over a signal line. Japanese Patent Laid-open No. Hei 9-325905 illustratively discloses one such storage controller.
Techniques have been known recently which substitute a fibre channel interface for the SCSI (Small Computer System Interface) between a host computer and a storage controller. Illustratively, Japanese Patent Laid-open No. Hei 10-333839 discloses techniques for connecting a storage controller with a host computer using a fibre channel interface. The disclosed storage controller is designed for dedicated use with a host computer having a fibre channel interface.
The techniques disclosed in the above-cited Japanese Patent Laid-open Nos. Hei 11-7359 and Hei 9-325905 have one disadvantage: the storage controller as a whole has its performance constrained by the performance of a single control processor that handles I/O requests from host computers. Another disadvantage is that a disabled control processor will prevent host computers from using the storage controller. In particular, since today""s fibre channels are capable of transferring data at speeds as high as 100 MB/S, the performance of the control processor can be an impediment to taking advantage of the high data transfer rates offered by fibre channels.
The techniques disclosed in the above-cited Japanese Patent Laid-open No. Hei 10-333839 relate to a storage controller for exclusive use with fibre channel interfaces. That is, the proposed storage controller is incapable of connecting with a host computer having a SCSI interface.
It is therefore an object of the present invention to provide a storage subsystem and a storage controller adapted to take advantage of high data transfer rates of fibre channels while offering enhanced reliability and availability.
It is another object of the present invention to provide a storage subsystem and a storage controller capable of connecting with a plurality of host computers having multiple different interfaces.
In carrying out the invention and according to one aspect thereof, there is provided a storage subsystem or a storage controller for controlling transfer of input/output data to and from a lower level storage medium drive unit in response to input/output requests received from a higher level external entity. The storage subsystem or storage controller comprises: at least one external interface controller for receiving the input/output requests from the higher level external entity in accordance with a type of interface with the higher level external entity; at least one control processor which processes the input/output requests; and a loop of fibre channel interfaces interposed between the external interface controller and the control processor so as to serve as a channel through which information is transferred therebetween.
In a preferred structure according to the invention, the interface of the external interface controller interfacing to the higher level external entity may be a fibre channel interface. In another preferred structure according to the invention, the external interface controller may be capable of interface conversion between an interface which interfaces to the higher order external entity and which is different from a fibre channel interface on the one hand, and a fibre channel interface on the other hand.
Other objects, features and advantages of the invention will become more apparent upon a reading of the following description and appended drawings.